soma - 26-5-2017 at 00:51
With a mixture of hexane and ethyl acetate as eluant, would the mixture tend to separate with the ethyl acetate going faster on a silica gel tlc
plate?
Sigmatropic - 26-5-2017 at 01:03
I believe EtOAc overloads the plate immediately and thus does not separate into a secondary solvent front.
I have seen instances where a secondary solvent front is created with much more polar eluents (MeOH in DCM, H2O in MeCN(IIRC) and some mixture of
H2O:EtOH:EtOAc). This is usually a PITA as the results obtained with such a secondary solvent front on the TLC do not translate in any way, shape or
form to colomn chromatography.
Perhaps TLC plates have more loading capacity for these more polar compounds compared to the relatively apolar EtOAc.
Edit: Or perhaps the separation between Pet. Ethers and EtOAc very small and is of no practical importance.
[Edited on 26-5-2017 by Sigmatropic]
Metacelsus - 26-5-2017 at 05:34
Hexanes/ethyl acetate does not separate to any detectable degree when traveling up a TLC plate (assuming, of course, that the atmosphere around the
plate is already saturated with solvent vapor such that there is no net evaporation).